Hydraulic drive V's trad' propshaft and gearbox

[Proper Job]

I need to make some decisions in the not to distant future about a gearbox/drive arrangement for the National D3.

 

I have been toying with the idea of hydraulic drive.

 

The advantages as I see it are:

No alignment issues

No long propshaft running under the Boatmans cabin (also more headroom due to no raised floor)

Easy to fit a pump unit to the end of the engine (?)

 

Obviously there must be a number of disadvantages or everyone would be fitting them as standard. What are they?

 

How do you deal with axial thrust at the motor/prop end?

 

Suppliers?

 

Answers on a postcard please.

[Endeavour]

Try ARS Anglian Diesels Ltd who are always very helpful - 01508 520555. They could design and supply the full system.

[Yamanx]

Hi, I have hydraulic drive on my cruiser stern.

 

There are other advantages as well as those you describe, being able to go from flat out in forward to flat out in reverse as fast as you like without any ill effects on the drive train.

 

There are disadvantages, hydraulic oil is 'orrible messy stuff and no matter what you do you will come into contact with it, it will create some contamination somewhere.

 

The thrust is the same as any other drive.

 

There is a remote sort of feeling when using hydraulic drive, difficult to explain but sort of like driving an automatic car.

 

If the prop gets snagged theres nothing to break, the oil pressure will rise and the valve will just blow off back to tank.

 

On mine theres a drag that is fairly annoying when in neutral it can be near impossible to stop the prop for turning, but that may be a worn valve, unfortunately the valve is built into the pump housing and not readily accessable.

 

Getting the right size prop can be total guess work, even the prop gurus couldnt help me there and I've ended up with one thats a tad too small, or not enough pitch.

 

You can put any rotation of prop you want, just change the pipes over.

 

The "power" to the prop remains the same whether running fast or slow as the pressure is not relient on engine speed, just the flow.

[Proper Job]

Try ARS Anglian Diesels Ltd who are always very helpful - 01508 520555. They could design and supply the full system.

Emailed them at lunch time and got a response with a softcopy of their catalogue by close of business. All I've got to do is work out what you need!